The disclosure of Japanese Patent Application No. 2001-80924 filed on Mar. 21, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a filter that is formed so as to have a shape substantially identical to a shape of a forming surface by extruding semi-molten fibers to the forming surface, and also relates to a production method for the filter, a production apparatus for producing the filter, a forming die for the filter, and a forming assembly for forming the filter.
2. Description of Related Art
A sheet-shaped non-woven fabric is formed by receiving semi-molten fibers extruded from a spinning nozzle on a flat surface, such as a metallic mesh or the like, and reeling the layer of fibers formed on the metallic mesh or the like. Thus, a non-woven fabric is formed. In order to produce a filter from such a non-woven fabric, it is necessary to perform the steps of cutting the non-woven fabric into a predetermined shape and folding and adhering the cut pieces.
In order to omit the aforementioned steps of cutting, folding, adhesion, etc., a filter 80 is often formed by producing from a metallic mesh or the like a forming die 90 that has a forming surface 92 that is shaped substantially identically to the filter 80, and extruding semi-molten fibers F from a spinning nozzle onto the forming surface 92 of the forming die so as to form a layer as shown in FIGS. 15A and 15B. FIG. 15B is a sectional view taken on line 15Bxe2x80x9415B in FIG. 15A.
However, in the above-described method in which semi-molten fibers F are extruded onto the forming surface 92 shaped substantially identically to the filter 80, the amount of fibers F layered on upstanding surface portions 92k that are steep slope portions of the forming surface 92 becomes considerably less than the amount of fibers F layered on bent portions 92n or gentle slope portions 92m of the forming surface 92. Therefore, a side plate portion 86 of the filter 80 formed by the upstanding surface portions 92k of the forming surface 92 has a considerably smaller fiber density than an accordion plate portion 84 of the filter 80 formed by the gentle slope portions 92m and the like of the forming surface 92. That is, the side plate portion 86 of the filter 80 has a rough grain of fibers, and tends to allow dust leakage, in comparison with the accordion plate portion 84.
It is an object of the invention to reduce dust leakage through fibers laylered on upstanding portions of the forming surface.
A first aspect of the invention relates to a production method for producing a filter that has a shape substantially identical to a shape of a forming surface, by extruding semi-molten fibers to the forming surface, the production method comprising the step of gathering the fibers toward an upstanding surface portion of the forming surface when extruding the semi-molten fibers to the forming surface.
According to the first aspect, when semi-molten fibers are extruded to the forming surface, fibers are gathered to the upstanding surface portion of the forming surface. Therefore, a sufficient amount of fibers can be layered on the upstanding surface portion. Hence, the layering amount of fibers on the upstanding surface portion of the forming surface will not become considerably smaller than the layering amounts on other portions of the forming surface. Thus, the grain of fibers of the side plate portion of the filter formed by the upstanding surface portion does not become rougher than that of other portions of the filter. Therefore, dust leakage through the side plate portion becomes unlikely.
A second aspect of the invention relates to a production method for producing a filter that has a shape substantially identical to a shape of a forming surface, by extruding semi-molten fibers to the forming surface, the production method comprising the step of reducing gaps between fibers layered on the upstanding surface portion of the forming surface after the semi-molten fibers are extruded to the forming surface. Therefore, the grain roughness of the side plate portion of the filter can be made less than or equal to the grain roughness of the filtering portion, so that dust leakage through the side plate portion of the filter can be reduced.
A third aspect of the invention relates to a production method for producing a filter that has a filtering portion for filtering a fluid, and a side plate portion that closes two opposite sides of the filtering portion, by providing a frame body that becomes the side plate portion, and disposing inside the frame body a forming surface for forming the filtering portion, and extruding semi-molten fibers to the frame body and the forming surface. Therefore, it is easy to set the grain roughness of the side plate portion of the filter at a desired value, and it is possible to reduce the dust leakage through the side plate portion.
A fourth aspect of the invention relates to a filter produced by any one of the first to third aspect described above. This filter reduces the dust leakage through the side plate portion of the filter.
A fifth aspect of the invention relates to an apparatus for producing a filter, comprising a conveyor that carries and conveys a forming die having a forming surface for forming the filter, an extruder that extrudes semi-molten fibers to the forming die carried on the conveyor, and a device that gathers the fibers toward an upstanding surface portion of the forming surface when the extruder extrudes the semi-molten fibers to the forming die. Using this apparatus, a sufficient amount of semi-molten fibers can be layered on the upstanding surface portion of the forming die.
A sixth aspect of the invention relates to a forming die for forming a filter, including a slope surface portion for forming a filtering portion of the filter, and an upstanding surface portion for forming a side plate portion of the filter that closes two opposite sides of the filtering portion. A slope angle of the upstanding surface portion relative to a horizontal plane is set smaller than or equal to a slope angle of the slope surface portion relative to the horizontal plane. Therefore, it becomes possible to layer on the upstanding surface portion an amount of semi-molten fibers that is greater than or equal to the amount of semi-molten fibers layered on the slope surface portion.
A seventh aspect of the invention relates to a forming assembly that has a forming surface, and that forms a filter which has a filtering portion for filtering a fluid and a side plate portion that closes two opposite sides of the filtering portion, by extruding semi-molten fibers onto the forming surface. The forming assembly has a frame body that becomes the side plate portion, and a forming die disposed inside the frame body, for forming the filtering portion of the filter. If this forming assembly is used, the frame body becomes the side plate portion of the filter. Therefore, the grain roughness of the side plate portion can be adjusted based on the frame body.
A eighth aspect of the invention relates to a filter formed so as to have a shape substantially identical to a shape of a forming surface by extruding semi-molten fibers to the forming surface. The filter has a filtering portion for filtering a fluid, and a side plate portion that closes two opposite sides of the filtering portion. A grain roughness of the side plate portion is less than or equal to a grain roughness of the filtering portion. As the grain roughness of the side plate portion is less than or equal to the grain roughness of the filtering portion, the dust leakage through the side plate portion of the filter is reduced.
An ninth aspect of the invention relates to a filter formed so as to have a shape substantially identical to a shape of a forming surface by extruding semi-molten fibers to the forming surface. The filter has a filtering portion for filtering a fluid, and a side plate portion that closes two opposite sides of the filtering portion. An air flow resistance of the side plate portion is greater than or equal to an air flow resistance of the filtering portion. The increased air flow resistance of the side plate portion reduces the amount of air that flows through the side plate portion, and therefore reduces the dust leakage through the side plate portion. The air flow resistance of the side plate portion can be made greater than the air flow resistance of the filtering portion by, for example, forming the filter through the use of the forming die described in conjunction with the seventh aspect of the invention.
A tenth aspect of the invention relates to a filter formed so as to have a shape substantially identical to a shape of a forming surface by extruding semi-molten fibers to the forming surface. The filter has a filtering portion for filtering a fluid, and a side plate portion that closes two opposite sides of the filtering portion. A thickness of the side plate portion is greater than or equal to a thickness of the filtering portion. Therefore, since the thickness of the side plate portion is greater than or equal to the thickness of the filtering portion, the dust leakage through the side plate portion is reduced.